Alkali and heat resistant insulation



Patented Mar. 13, 1923.

UNITED STATES v A 1,448,386 PATENT OFFICE.

GORDON A. BURR AND JOHN R. 'MOCLAIN, OF WILKINSBURG, AND LESLIE E. FROST, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ALKALI AND HEAT RESISTANT INSULATION.

No Drawing.

To all whom it may concern:

Be it known that we, GORDON A. Bonn, a citizen of the United States, and a resident of Wilkinsbur in the county of Allegheny and State of Tennsylvania; JOHN R. Mo-

CLAIN, a citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania; and LESLIE E. F ROST, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Alkali and Heat Resistant Insulations, of which the following is a specification.

Our invention relates to electrical insulat ing material, more especially to composite insulation formed from fibrous sheet material and "a plurality of insulating compounds.

It is among the objects of our invention to provide a material which shall have a relatively high dielectric value, which shall be alkaliand heat resistant, which shall be mechanically strong and have superior physical properties, and which may be uniformly produced in a simple manner.

Insulating materials formed of fibrous materials and suitable binders, such as insulating varnish, shellac, phenolic condensation products and the like, have commonly been formed into various shapes, such as tubing, channel members, rods and sheet material, by impregnating or treating fibrous materials, such as fabric, paper, asbestos and the like, with the binding agents and forming them into desired shapes under heat and pressure. I

These materialsare applicable to various usesin accordance with their characteristics and the service requirements, but it has been difficult to obtain a unitary material which posseses a number' of desirable qualities that would adapt it for use as an electrical insulating material generally.

We propose to provide a material which possesses such qualities to a high degree by providing a layer of fibrous sheet material which is treated, as by impregnating or coating, with a suitable insulating varnish, such as asphaltum in combination with a suitable drying oil, and is then impregnated or coated with a phenolic condensation product.

In practising our invention, the fibrous Application filed September 16, 1921. Serial No. 501,178.,

sheet material is unreeled from a supply roll intova tank containing asphaltum var- IllSh .and is then chamber. The treated sheet is then passed through a tank containing a'phenolic condensation product in solution with a suitable solvent and the solvent is driven ofi' after treating by passing the sheet material through a drying chamber.

The heat treating or drying process also drives 01f any moisture present in the material due to atmospheric humidity, and the compound treated sheet may then be formed by molding, with heat and pressure, into the shape desired.

The asphaltum varnish permeates and envelopes the composite material, giving it greater flexibility than treatment with ordinary shellac or a phenolic condensation product, and the additional treatment with the phenolic condensation product greatly increases its mechanical strength.

It is well known that'a natural or petroleum asphalt, in combination with drying oils, has excellent insulating properties and resistance to alkali. By treating paper or fabric with such varnish and drying the varnish, then treating the sheet with a condensation product, we obtain a treated material which may be used as a base for different composite articles, such' as tubes, rods, channel members andsheets of various forms.

These articles may be formed in the usual manner, as by superposing a plurality of layers of the treated material and subjecting them to relatively high pressure and temperatures.

Tubes of any desired thickness and diameter may be formed by spirally winding a plurality of superposed convolutions of the material specified above about a heated mandrel between a plurality of pressure rolls. Articles formed in this manner are highly insulating, acid and alkali resistant and are mechanically strong and possess superior flexibility and resistance to deterioration' when subjected to high temperatures for long periods of time.

This material is also heat and are resistant and may be applied to switchboard passed through a drying sulating materials formed in accordance therewith have the combined quallties of other well known materials and that they possess many of their desirable characteristics.

Although we have described a specific embodiment of our invention, it will be obvious to those skilled in the art that vari-. ous changes may be made therein without departing from the principles herein set forth, as, for instance, any suitable fibrous sheet material may be employed in place of those mentioned. Cther suitable varnishes may be substituted for the asphaltum material, or shellac, casein, blood glue or other suitable binding agent may be substituted for the phenolic condensation product.

Vfe claim as our invention:

1. Composite sheet material comprising a layer of fibrous sheet material treated with insulating Varnish and a phenolic condensation product.

2. Composite sheet material comprising a layer of fibrous sheet material impregnated with insulating varnish and coated with a phenolic condensation product.

3. Composite sheet material comprising a layer of fibrous sheet material coated with insulating varnish and coated with a phenolic condensation product.

4. Composite sheet material comprising a layer of fibrous sheet material treated with asphaltum in combination with a drying oil and coated with a phenolic condensation product.

5. Composite sheet material comprising a layer of fabric treated with asphaltum in combination with a drying oil and coated With a phenolic condensation product.

6. Composite sheet material comprising a layer of paper treated with asphaltum in combination with a drying oil and coated with a phenolic condensation product.

7. Composite sheet material comprising a plurality of layers of fibrous sheet material treated with an insulating varnish and a phenolic condensation product consolidated under heat and pressure.

8. Composite sheet material comprising a plurality of superposed layers of fibrous sheet material impregnated with an insulatmg varnish and a phenolic condensation product consolidated under heat and pressure.

9. Composite sheet material comprising a plurality of superposed layers of fibrous Laaaesc sheet material treated with asphaltum and a phenolic condensation product consolidated under heat and pressure.

10. The method of forming composite sheet material which comprises providing a sheet of fibrous material, treating said sheet material with an insulating varnish, passing said material through a drying tower, coating said treated sheet with a phenolic condensation product and passing said sheet through a drying chamber to drive ofi the moisture and solvent.

11. The ,method of forming composite sheet material which comprises providing a sheet of fibrous material, treatin said sheet material with an insulating varnish, passing said material through a drying tower, coating said treated sheet with a phenolic condensation product, passing said sheet through a. drying chamber to drive off the moisture and solvent and applying heat and pressure thereto to consolidate the same.

12. The method of forming composite sheet material which comprises providing a plurality of superposed layers of fibrous sheet material, treating the same with asphaltum in combination with a drying oil, coating said treated material with a phenolic condensation product, drying said treated layers and applying heat and pressure thereto to consolidate the same.

13. The method of forming composite sheet material which comprises providing a plurality of superposed layers of fabric,

treating the same with asphaltum in com-' bination with a drying oil, coating said treated material with a phenolic condensation product, drying said treated layers and applying heat and pressure thereto to consolidate the same.

14. The method of forming composite sheet material which comprises providing a plurality of superposed layers of paper,

treating the same with asphaltum in combination with a drying o-il, coating said treated material with a phenolic condensatlon product, drying said treated layers and applying heat and pressure thereto to consolidate the same.

lln testimony whereof, we have hereunto subscribed our names this 3rd day of Sep tember, 1921;

LESL'IE E. 

